It is known to secure a payload pallet in the loading bay of a space shuttle which forms a fixed structure in which the pallet is secured by releasable clamps in the directions of the x- and z-axis of a three dimensional coordinate system defined by the fixed structure of the space shuttle. The forces in the y-direction are transferred from the pallet into the fixed structure through a yoke shaped holding structure known as a keel yoke assembly (KYA).
Orbital space stations such as the International Space Station (ISS) which moves on an orbit relatively close to earth, must be supplied with all sorts of supplies. In the case of the ISS the supplies are secured primarily on a pallet mounted in the cargo bay of the space shuttle which transports the supplies with the pallet to the orbital station. Conventionally, the pallet and its support structure remain in the shuttle during the entire mission. The pallet is conventionally an unpressurized cargo pallet (UCP). The keel yoke assembly secures the pallet in the cargo bay and takes up forces in the direction of the y-axis, namely crosswise to the cargo bay of the shuttle. The keel yoke assembly rigidly secures the pallet to the shuttle and the pallet cannot be separated from the shuttle once in orbit. The supplies must be individually transferred from the pallet in the cargo bay to the space station. Such a mounting of the pallet in the space shuttle is, for example, described in German Patent Publication DE 198 50 699 C1.
Future missions still in the planning stage provide for the removal of the payload pallet from the shuttle while leaving the keel yoke assembly in the shuttle and docking the pallet to the outside of the space station to simplify transfer of supplies. In this connection it is known to secure removable payload items to the keel with the help of a keel pin or by a so called trunnion holding the loads in the x- and y-directions and with at least one port side pin and one starboard pin for holding the pallet in the x- and z-directions. In that case it is possible to release the payload solely by opening the standard holding clamps provided in the shuttle. With the clamps open the payload can be removed from the shuttle and fixed again in the shuttle by closing the clamps. Such mountings are known from European Patent Publication EP 0 256 001 B1 and from U.S. Pat. No. 4,303,214. This type of mounting can, however, not be realized when it is intended to secure payload items to the top surface of the pallet and to the underside of the pallet. For this purpose it would be necessary to temporarily remove the pallet from the shuttle in order to completely unload the load items from both sides of the pallet. In such a case the forces effective in the direction of the y-axis cannot be introduced, as is conventional, directly from the payload through struts into the keel of the shuttle.